The Chi River (Thai: แม่น้ำชี, RTGS: Maenam Chi, pronounced [mɛ̂ː.náːm tɕʰīː]; Northeastern Thai: แม่น้ำซี, pronounced [mɛ̄ː.nâːm sîː]) is the longest river flowing wholly within Thailand. It is 765 kilometres (475 mi) long but carries less water than the second longest river, the Mun. The name of the river is "Mae Si" ([sîː]) in the Isan and Lao languages of the region, being transliterated as "Chi" in Bangkok-Thai. In wet seasons there are often flash floods in the floodplain of the Chi River basin. The Chi River is a major tributary of the Mun River which then flows into the Mekong.
